1. Field of the Invention
The present invention relates to the field of electrical contactors and similar devices. More particularly, the invention relates to a housing structure for an electrical contacting device having an electromagnetic actuator assembly in a first portion and an electrical switch or contact assembly in a second portion. The invention also relates to a method for isolating operative assemblies in such contacting devices.
2. Description of the Related Art
A variety contacting devices are known and are commercially available for placing a source of electrical energy in electrical connection with a load, and for interrupting a current carrying path therebetween. Electrical contactors, for instance, are known for both single-phase and multiple-phase circuits. Such contactors generally include an actuating assembly mechanically connected to a switch or contactor structure. In remotely-controllable contactors of this type, it is commonplace to provide an electromagnetic actuating assembly which operates either on alternating current or direct current. The actuating assembly is energized by a control signal, such as from a remote controller. Electrical current through the actuating assembly causes movement of an armature under the influence of an electromagnetic field generated by an actuating coil. A carrier coupled to the armature, moves movable contacts in the contact assembly to open or close a current-carrying path through the device, depending upon whether the device is electrically wired to be normally-open or normally-closed.
In industrial contactors of the type described above, the elements of the contact assembly may be subjected to a large number of opening and closing cycles during their useful life. During each opening and closing cycle, arcs may be produced between movable and stationary contacts in the contact assembly. Because these arcs may deteriorate both the contacts, as well as surrounding structures, various techniques have been devised to reduce the tendency of the contact assembly to arc during opening and closing, or to control or dissipate the arcs when produced. Such arcs may be particularly harmful in multi-phase contactors, wherein progressive damage to the contactor assembly components or housing can significantly reduce the useful life of the device, and possibly lead to phase-to-phase short circuits.
To facilitate assembly of their component parts, conventional contactors typically include a base housing section for holding the actuating assembly, and an upper housing section for the contactor assembly: The base housing section receives the actuating assembly, typically through an opening in its lower end. The upper end of the base housing section is provided with apertures for a carrier which connects the actuating assembly to the contact assembly. The contact assembly is then positioned in,the upper housing section. The two housing sections are joined and secured to one another during assembly of the device.
In addition to providing several constituent parts, conventional housing structures are typically made of materials adapted to accommodate the anticipated working conditions of the contactor, particularly high temperatures during opening and closing cycles. Despite improvements in contactor design which somewhat limits arcing or which dissipates heat generated by the arcs, significant temperatures are often generated during such cycles. Nor only must the housing sections, particularly the upper or contact assembly housing, withstand such temperatures, they must also provide some degree of isolation of interior regions of the contactor from the exterior to prevent hot gasses and plasma from escaping from the housing, as well as isolation between power phase sections to prevent phase-to phase short circuits.
To accommodate the high temperatures generated during opening and closing cycles, conventional contactor housings are typically made of metals and thermosetting plastics. Certain of these housings may be made of dissimilar materials, such as a metal base structure for supporting the actuating assembly on a mounting surface or plate. A thermosetting plastic upper portion is then added to the metal base to house the contactor assembly.
Conventional housing structures of the type described above are not without drawbacks. For example, because multiple sections are employed in the housing, gaps may exist in the assembly between the housing sections, or may develop over time. Under the influence of high pressures and temperatures generated during operation, these gaps may ultimately lead to short circuits or accelerated degradation of the contactor housing. Moreover, conventional metal and thermosetting plastic housings can be fairly expensive to manufacture, particularly in smaller production runs and in larger sized devices.
There is a need, therefore, for an improved housing for electrical contact devices. In particular, there is a need for a novel technique for supporting and electrically isolating component assemblies of a contactor which is both economical to manufacture, and which provides improved electrical isolation capabilities.
The invention provides an innovative approach to the design of a contactor housing which responds to these needs. The approach includes the formation of a unitary housing structure which includes both a housing portion for the actuating assembly, as well as a housing portion for a contact assembly. The unitary structure provides integral dividing partitions between the actuating and contact assemblies. In a multi-phase contactor, the housing also provides integral partitions between phase sections to avoid exchanges between gases within the housing which may lead to short circuits. Where structures in the contactor effectively limit the anticipated temperature rise during opening and closing cycles, the novel housing is preferably made of a thermoplastic material which can be molded to form the unitary structure. The housing may also include features for influencing the operation of the actuating assembly and the contact assembly, such as integral chambers for cushioning movement of the assemblies during opening and closing.
Thus, in accordance with the first aspect of the invention a housing is provided for an electrical contactor. The contactor includes an actuating assembly and a contact assembly. The actuating assembly is operative to selectively displace a movable contact in the contact assembly between an open position and a closed position. The housing includes a unitary shell having peripheral walls for receiving and at least partially surrounding the actuating assembly and the contact assembly. The housing also includes a transverse internal partition integral with the shell for separating the actuating assembly from the contact assembly. In a preferred configuration, the housing also includes internal phase partitions integral with the shell and the transverse internal partition for separating power phase sections in which the contact assembly will be disposed. The transverse internal partition may include at least one aperture for a transmission member used to displace the contact assembly. The housing is preferably made of a moldable thermoplastic material. Moreover, the transverse internal partition may form a cushioning cavity for limiting the rate of displacement of a portion of the contact assembly.
The invention also provides an electrical contactor including an electromagnetic operator, a polyphase contact portion, a unitary housing body, and a cap. The polyphase contact portion includes parallel phase sections, each having a pair of stationary contacts and a movable contact element displaceable with respect to the stationary contacts to complete and interrupt a current carrying path through the phase section. The unitary housing body defines a base cavity for receiving the electromagnetic operator and a plurality of contact cavities for receiving respective phase sections. The base cavity is separated from the contact cavities by an integral transverse partition. The contact cavities are separated from one another by integral phase partitions. The cap is configured to be secured to the body and to fit over the contact cavities. Again, the housing body is preferably made of a moldable thermoplastic material. Moreover, the transverse partition is preferably contiguous with the phase partitions. The housing body may include terminal apertures for each phase section for receiving phase terminals.
In accordance with a further aspect of the invention, an electrical contactor includes an electromagnetic operator, a polyphase contact portion, a central housing, and a cap. The contact portion includes, in turn, several phase sections. Each phase section includes a pair of stationary contacts and a movable contact element displaceable with respect to the stationary contacts under the influence of the electromagnetic operator. The central housing is made of a moldable thermoplastic material and forms a base cavity for receiving the operator and a plurality of contact cavities for receiving respective phase sections. The base cavity is separated from the contact cavities by a transverse partition. The contact cavities are separated from one another by phase partitions. The cap is configured to be secured to the body and to fit over the contact cavities. The transverse and phase partitions may be integrally formed with the central housing, to prevent or reduce the potential for exchange of gases between the operator and the contact elements of the device, and between the separate contact structures in the base sections.
In accordance with yet another aspect of the invention, a method is provided for isolating operative components of an electrical contactor. The contactors of the type include an operator and a contact assembly having movable contacts selectively displaceable with respect to stationary contacts to complete current carrying paths through the contactor. In accordance with the method, a unitary housing body is provided, including peripheral walls and an integral transverse partition defining a base cavity and a contact cavity. The operator is positioned within the base cavity. The contact assembly is positioned within the contact cavity, the transverse partition isolating the operator from the contact assembly. Covers are then secured to the base and contact cavities. In accordance with a particularly preferred embodiment of the method, the contact assembly includes a plurality of phase sections, and the method includes the step of forming phase partitions within the contact cavity, the phase partitions being contiguous with the transverse partitions. Terminal apertures may also be formed in the housing body and a partition may be formed on an external peripheral surface of the housing body between adjacent terminal apertures. The unitary housing body may be formed of a thermoplastic material.